A wellbore may be drilled to locate and produce hydrocarbon-based fluids. The wellbore is drilled by a downhole drilling tool having a drill bit which is advanced into the formation to form a wellbore. As the drilling tool is advanced, drilling mud is pumped through the drilling tool and out through the drill bit to cool the drilling tool and to carry away cuttings. The fluid exits the drill bit and circulates back up to the surface before being recirculated back down to the drilling tool. The drilling mud also may be used to form a mud cake lining the wellbore.
During the drilling operation, various downhole evaluations may be performed to determine characteristics of the wellbore and/or surrounding formation. Depending on the application, the downhole evaluations may be conducted with devices contained in the drilling tool. However, the devices also may be deployed downhole via a wireline after the drilling tool has been removed. Examples of devices employed in performing downhole evaluations may include probes, packers, fluid analyzers, and/or sensors to obtain and measure downhole characteristics which may indicate the presence of hydrocarbons.